The Complexity of Head Movement is Correlated with Learning about Affordances for Walking.

We asked whether the quantitative kinematics of standing postural activity might be related to short-term learning of affordances. Standing participants viewed a narrow path for 15 s, and then gave perceptual reports about the distance that they could walk along the path while wearing a weighted vest (novel affordance) or while not wearing the vest (familiar affordance). In a control condition, participants gave perceptual reports about egocentric distance along the path. During the 15 s viewing intervals, we measured the kinematics of head and torso movement as standing participants made a series of 12 perceptual reports. Perceptual reports improved across trials, but only in the condition in which participants were asked to perceive a novel affordance. The dynamical complexity of head movement changed across trials as participants gave perceptual reports about the novel affordance, but did not change systematically when perceiving a familiar affordance, or a non-affordance egocentric distance. We argue that the dynamical complexity of postural activity may have served an exploratory function supporting the learning of a novel affordance. Our results are consistent with the broader hypothesis that affordances are learned through active engagement with the environment, rather than (for example) through abstract cognitive processing.